Hello Steve,
I have no idea what happened to your congo red on the left. It has a darker colour already in water solution. My congo red looks like the one on the right, and it doesn't change colour with KOH. I have congo red dissolved in water, in ammonia and in SDS - the colour is always the same.
I also tried to create a solution of congo red in other tenside than SDS to avoid the percipitation that occures when using cngo red in SDS together with KOH. I tried Invadin, which is no longer available and may be replaced by Triton X (Octylphenol), but all this detergents did not make the solution better in my opinion. congo red in Triton X had a slightly more pinkish hue compared to the other congo red solutions.
All these detergents (SDS, Invadin, Triton X, ammonia) have the aim to soften the tissue of your preparation, which usually is not necessary, at least not in fresh material. My favorite is still congo red in ammonia.
all the best,
Andreas